The detailed background of the present invention is disclosed in U.S. Pat. No. 5,301,760 granted Apr. 4, 1994, which is incorporated herein by reference. In summary, a completed lateral or horizontal drainhole is produced by cutting or milling a window through the casing in a well borehole using a whipstock to provide the desired direction, the lateral or horizontal drainhole is completed by sealing a pipe string or liner which extends from the wellbore at least through the curved portion of the lateral, providing a sealed interface between the cased wellbore and the lateral; and the cased wellbore is restored by removing any sealant and/or pipe in the cased portion of the wellbore with a burning shoe.
The system of the present invention is directed to the selective re-entry to a completed lateral or horizontal drainhole for the purpose of cleanout operations, sand control methods, stimulation, and/or any other operation which is carried out in the lateral.
U.S. Pat. Nos. 5,311,936; 5,318,121; 5,318,122; 5,322,127; 5,325,924; 5,353,876; and 5,388,648, all patents having essentially the same disclosure and assigned to Baker Hughes Incorporated, disclose a number of methods and apparatus for sealing the juncture between a vertical well and one or more horizontal wells. The disclosure of U.S. Pat. No. 5,322,127 is incorporated herein by reference.
U.S. Pat. No. 4,396,075 discloses a method for drilling and completing multiple branch wells extending from a main generally vertical hole.
U.S. Pat. No. 4,415,205 discloses a method and apparatus to complete multiple branch wells using separate drill and casing templates.
U.S. Pat. No. 4,573,541 discloses a multi-drain drilling and petroleum start-up device.
U.S. Pat. No. 4,742,871 discloses device for positioning a tool within a wellbore flow string.
U.S. Pat. No. 5,330,007 discloses a template and process for drilling and completing multiple wells.
In all the patents cited above, the re-entry into a lateral or horizontal borehole requires the structure used in producing the lateral. None of the patents disclose the re-entry of a completed lateral where the structure for making the lateral has been removed.